IgA nephropathy shortly follwed by seroconversion of positive anti-GBM antibodies and rapid progressive glomerulonephritis in a Chinese boy: coincidental overlap or pathogenic link?

BACKGROUND

Anti-glomerular basement membrane (anti-GBM) disease is a rare, aggressive autoimmune disorder that seldom coexists with IgA nephropathy (IgAN). The development of anti-GBM disease secondary to IgAN in pediatric patients-specifically with confirmed seroconversion-is exceptionally rare. We present a case of a 14-year-old boy who developed anti-GBM disease shortly after an initial diagnosis of IgAN.

CASE PRESENTATION: A 14-year-old male presented with a 10-day history of gross hematuria. Initial evaluation showed normal renal function and negative anti-GBM antibodies. The initial renal biopsy confirmed IgAN (Lee grade V; Oxford classification M1E0S1T0-C2). Despite receiving continuous Nefecon monotherapy (16 mg/day) combined with irbesartan 150 mg/day, his renal function deteriorated rapidly four months later, with serum creatinine (Scr) surging from 65 to a peak of 665 µmol/L. Repeat serological testing revealed a significant seroconversion of anti-GBM antibodies from negative to strongly positive (> 8.0 AI). A second renal biopsy demonstrated devastating progression, with 100% fibrocellular crescent formation and intense linear IgG deposition along the glomerular capillary walls. The patient received an intensified regimen consisting of plasmapheresis, hemodialysis, and cyclophosphamide pulse therapy. Following treatment, his anti-GBM antibodies turned negative, and renal function stabilized without dialysis, though it did not return to the pre-morbid baseline.

CONCLUSIONS

We report a pediatric male case in whom anti-glomerular basement membrane disease developed secondarily during the clinical course of IgA nephropathy. This case strongly suggests that in patients with newly diagnosed chronic glomerulonephritis, such as IgA nephropathy, a high index of suspicion for concurrent autoimmune diseases including anti-glomerular basement membrane disease should be maintained when rapid progression of glomerulonephritis occurs.